Motion Planning and Control for FRC - FIRST Championship Conference Session

[Jared Russell]

Originally Posted by Joe Ross

What level of math are you planning to get into?

There will be some advanced high school level math, but nothing more than that.

There will be no root locus plots, Laplace transforms, or serious state-space math. Those are certainly useful tools, but there are already textbooks devoted to them. There will be algebra, some calculus, and some light differential equations.

We will be presenting some ideas whose derivations involve all of the above concepts, but we intend to be pragmatic and focus on shedding light on the intuition behind the math. We will also talk about best practices and FRC "tribal knowledge" to help overcome common problems in implementing motion control on our robots.

[NWChen]

Originally Posted by Jared Russell

We will make sure that, one way or another, this talk gets recorded.

Awesome, thank you guys. We worked on a spline-based path generator after being inspired by 254's, but it never got implemented beyond an interface for creating curves. Would love to see how to take that tool through the next steps.

[AlexD744]

So many good conferences on wednesday and I'm not coming til Thursday

Thank you for ensuring it's recorded, will definitely check it out!

[Bryce Paputa]

I wish I didn't have a robot to put back together and drive once I get there...

I guess a recording will suffice.

[kgzak]

I was just wondering where/when/if the video recording would be available.

Thank you

[AlexanderTheOK]

I'm sure it will be up somewhere once these teams have breathing room after champs.

[Poseidon5817]

Seconding the request for the presentation recording. This would be a nice project for the off season, if we have time.

[Jared Russell]

Expect this to be posted some time this week.

[Jared Russell]

Thank you to all who attended our conference session. We were blown away by the number of people in the audience - several hundred FIRSTers were there and it was standing room only! This goes to show that the FRC community has quite an appetite for technical conference sessions, and I hope we can grow this part of the Championship Conferences substantially in the years to come.

As promised, here is the recording of the session (in standard Cheesy Poof 4k of course): https://youtu.be/8319J1BEHwM

And here are the slides (with a couple of small corrections from the version used in the session): https://docs.google.com/presentation...e&delayms=3000

We hope that our session was useful! We know there are some things we can improve for future sessions. One request for anyone who attended: please feel free to PM or email me feedback so we can get better at this in the future. A major challenge in presenting on such a deep subject is hitting the right technical level - there were many levels of experience and expertise in the audience, and you don't want to alienate either end. Please tell us how we did!

[Abhishek R]

Originally Posted by Jared Russell

Thank you to all who attended our conference session. We were blown away by the number of people in the audience - several hundred FIRSTers were there and it was standing room only! This goes to show that the FRC community has quite an appetite for technical conference sessions, and I hope we can grow this part of the Championship Conferences substantially in the years to come.

As promised, here is the recording of the session (in standard Cheesy Poof 4k of course): https://youtu.be/8319J1BEHwM

And here are the slides (with a couple of small corrections from the version used in the session): https://docs.google.com/presentation...e&delayms=3000

We hope that our session was useful! We know there are some things we can improve for future sessions. One request for anyone who attended: please feel free to PM or email me feedback so we can get better at this in the future. A major challenge in presenting on such a deep subject is hitting the right technical level - there were many levels of experience and expertise in the audience, and you don't want to alienate either end. Please tell us how we did!

Thank you!

It may just be me, but are the slides private right now?

Edit: Never mind, doesn't like the mobile app for some reason.

[mman1506]

Originally Posted by Abhishek R

Thank you!

It may just be me, but are the slides private right now?

Just you

[Ether]

Originally Posted by Abhishek R

Thank you!

It may just be me, but are the slides private right now?

The download options do not work for me either :-(

[Asymons]

I've been avidly waiting for this .

Both links work for me perfectly. Perhaps the issue is resolved now or maybe try a different browser(I'm using chrome).

[Jared]

This is an awesome presentation - I'm our team had to miss it because we didn't have badges yet. I think the level of detail was pretty much perfect for an hour long presentation.

As you mentioned, the internet has lots of great papers describing the process:
http://www2.informatik.uni-freiburg....Sprunk2008.pdf

In the presentation, you talked about tuning ka and kv, which we found to be a frustrating process. We started with the method you describe with the robot's maximum velocity and maximum acceleration, but we found that these values of ka and kv only worked well when we ran aggressive and fast trajectories, and weren't as accurate with slower, less terrifying trajectories. kP for the feedback controller had to be increased to maintain accuracy, which caused the robot to oscillate if it was bumped off course. With different values of ka and kv, we could let the feedforward controller do most of the work and decrease kp to improve stability.

Our method to find kp and ka was to simply drive the robot in a straight line with varying speed, acceleration, and power, and record this information every 20 ms. I used a 4 sample moving average to get smooth data from the encoders.

I looked at two points in time that each had different velocity, acceleration, and power, and solved these two equations for ka and kv.

kv * v1 + ka * a1 = p1
kv * v2 + ka * a2 = p2

I repeated this process of selecting two points and solving the equations for 10 times, and averaged the values of ka and kv to get the actual gains.

This resulted in a slightly higher value of kv and a much higher value of ka than we got with the full acceleration test.

[GreyingJay]

Thanks again for putting this session on.

I am on the newbie end of the knowledge scale for this topic - I know about PID and I understood the basic concepts of motion profiling but it will take some further reading and research to figure out how to make it work for us. I think it was a bit above the heads of the freshmen students I brought with us but they were interested and following along as best they could. They can't wait to try out the code that has been made available.